Year 8 · Maths
Understand The Relationship Between Parallel Lines And Angles
What is the co-interior angle rule?
When a transversal crosses two parallel lines, co-interior angles lie between the parallel lines on the same side of the transversal and add to 180°. If one co-interior angle is 112°, the other is 180° − 112° = 68°. This rule only applies when the two lines are parallel.
| Angle pair | Rule | Worked example |
|---|---|---|
| Co-interior | Add to 180° | 112° + 68° = 180° |
| Alternate | Are equal | An alternate angle to 68° is 68° |
| Corresponding | Are equal | A corresponding angle to 112° is 112° |
Keep practising: Use the Year 8 Maths checklist
Year 8 learners practise angles in parallel lines alternate and corresponding angles.
The activities include Calculate Angles in Triangles and on Parallel Lines, Find Alternate and Corresponding Angles on Parallel Lines, Find Angles in Triangles and on Parallel Lines. The checked support below includes teach, video, worksheet, teaching. Open a resource in its provider's website and choose the format that best helps the learner explain the idea independently.
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Watch it explained
watch a video explanation
Oak video: Angles On Parallel Lines Traversed By A Straight Line
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Oak video: Alternate Angles
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Geometrical properties: polygons
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Oak lesson slides: Angles On Parallel Lines Traversed By A Straight Line
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Angles in Parallel Lines KS3 Resource Pack
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Angle Properties KS3 Walkthrough Worksheet
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Oak lesson slides: Corresponding Angles
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Oak lesson slides: Alternate Angles
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Oak worksheet: Angles On Parallel Lines Traversed By A Straight Line
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Oak worksheet: Corresponding Angles
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